1. Field of the Invention
The present invention relates to closures for chambers and, more particularly, to apparatus for moving and securing a door to an opening of a chamber which may be pressurized.
2. Description of the Prior Art
There exists a wide variety of chambers adapted for maintaining a desired level of pressure therewithin. An example of such a chamber is a sterilizer that operates under pressure during at least part of its cycle. To enable pressure to build within the chamber of, e.g., a sterilizer, it is necessary to provide a seal against fluid flow from the chamber to the atmosphere through the area between the perimeter of the chamber opening and the door of the sterilizer. Typically, such a seal is effected by disposing a sealing device between the perimeter of the opening and the door. The sealing device is usually attached to either the perimeter of the opening or the chamber door. Generally, one of two types of sealing devices is used to effect the fluid seal. The first type, a compression seal, requires that compressive force be exerted on the seal by the door and the perimeter of the opening to the chamber. The second type, a noncompressive seal, does not require the exertion of such a compressive force, but requires only that the seal contact the surfaces of both the perimeter of the opening and the door.
The conventional designs of closures for such sterilizers generally fall into several different categories. For example, one previous design of a sterilizer door closure system includes a bar mounted across the outer face of a door and extending from a vertical hinge on one side thereof to a horizontal "U"-shaped slot on the other. Such slot is intended to be engaged by a large pressure nut provided on a horizontally pivotal swing bolt. In operation, the door is pivoted about the hinge to a position in engagement with the opening of the chamber, the swing bolt is moved into the slot on the door bar and the pressure nut is rotated into compressing relation with the end of the door bar.
It must be noted, however, that various problems exist with such a system. First, as the compressive force generated by the pressure nut is caused to bear on only a localized area of the door bar, it is difficult to achieve an even sealing pressure around the entire perimeter of the door. Second, such a design requires many turns of the large pressure nut to achieve sealing. Such a time- and effort-intensive process causes excessive delays in the sterilization process which reduces the sterilizer's overall capacity. Also, the swing bolt/pressure nut design is necessarily limited to small pressure chambers because the design is unable to effect satisfactory sealing of a large opening and requires an inordinate number of turns of an effort applied to the pressure nut.
Another conventional door design for a pressurized chamber also includes a bar extending across the outside of the door. The door is supported by the bar which, in turn, is supported at one end by a loose fitting hinge. The door is secured to the opening of the chamber by means of a pin mounted on the chamber on the opposite side of the opening from the hinge. To operate such a door, the door is closed by means of a handle affixed to the door bar adjacent its free end and the door is lifted onto the pin adjacent the opening so that an aperture in the door bar engages the pin. A handwheel is then used to bring pressure onto the door and to urge it into sealing engagement with the chamber opening.
As will be appreciated, various problems are also present with such a door closure design. For example, due to the fact that a loose fitting hinge is required to allow the door to be lifted onto the pin, it is more difficult to achieve effective sealing with such design. Also, the requirement that a heavy pressure door must be manually lifted into engagement with the pin requires an inordinate amount of operator effort. Obviously, such a door closure design may only be employed on small pressure chamber doors due to the sealing considerations and the door weight which must be lifted.
Yet another pressure chamber door closure system includes a vertically slidable knife-type door which slides in vertical rails along the edges of the opening. This system is costly to manufacture as it requires the provision of a counterweight for the door. Also, a door closure system according to such a design is not suitable for usage on small chamber doors due to the excessive costs and additional parts associated therein.
A final example of a conventional closure for a pressure chamber, such as a sterilizer, includes a cluster of radial arms or bolts, one end of which is attached to a circular central hub upon which a threaded nut is mounted. The nut travels along a threaded doorpost which is mounted to the door plate. The door is closed tightly against the chamber by rotating a handwheel that is mounted on the threaded nut for several revolutions. An initial rotation of the handwheel causes the central hub to rotate and push the free ends of the radial arms into a frame mounted on the sterilizer shell and to secure the door in a position in which the door confronts the sterilizer opening, but in which the door does not seal the sterilizer. Further rotation of the handwheel pushes the door against the perimeter of the chamber opening.
The nut, the threaded doorpost and the associated closing apparatus are bulky and expensive to manufacture; further, since the mechanism must transfer the torque applied to the handwheel to a linear force exerted against the door through the threaded doorpost, the user must rotate the handwheel through a number of revolutions to secure the door against the perimeter of the chamber opening.
The subject invention is directed toward an improved apparatus for securing the door of a chamber capable of maintaining pressure within the chamber, such as a sterilizer, against the perimeter of the opening of the chamber which overcomes, among others, the above-discussed problems and which is effective to positively secure the chamber door while requiring a minimal amount of user effort.